package com.yu.thread10;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * Created by xiaolongyu on 15/4/13.
 */
public class CountDownLatchDemo {

    private static final int SIZE = 20;

    public static void main(String[] args) {

        ExecutorService exec = Executors.newCachedThreadPool();
        CountDownLatch latch = new CountDownLatch(SIZE);
        for(int i = 0; i < 10; i ++){
            exec.execute(new WaitingTask(latch));
        }

        for(int i = 0; i < SIZE; i ++){
            exec.execute(new TaskProtion(latch));
        }

        System.out.println("Launched all tasks");
        exec.shutdown();
//        exec.shutdownNow();
    }

}

class TaskProtion implements Runnable {
    private static int counter = 0;
    private final int id = counter ++;
    private static Random rand = new Random(47);
    private final CountDownLatch latch;

    public TaskProtion(CountDownLatch countDownLatch){
        this.latch = countDownLatch;
    }

    @Override
    public void run() {
        try {
            doWork();
            latch.countDown();
        } catch (InterruptedException e){
            System.out.println(this + " interrupted");
        }
    }

    private void doWork() throws InterruptedException {
        TimeUnit.MILLISECONDS.sleep(rand.nextInt(2000));
        System.out.println(this + " completed");
    }

    @Override
    public String toString(){
        return String.format("%1$-2d", id);
    }
}

class WaitingTask implements Runnable {
    private static int counter = 0;
    private final int id = counter ++;
    private final CountDownLatch latch;

    public WaitingTask(CountDownLatch countDownLatch){
        this.latch = countDownLatch;
    }

    public void run() {
        try {
            latch.await();
            System.out.println("Latch barrier passed for " + this);
        } catch (InterruptedException e) {
            System.out.println(this + " interrupted");
        }

    }

    @Override
    public String toString() {
        return String.format("WaitingTask %1$-2d", id);
    }
}